This invention relates to an improved technology for the separation of a rigid, transparent, conductively coated substrate and a flexible, transparent, conductively coated top sheet as used in an interactive information device such as a computer touch panel, a digitizer panel, a personal digital assistant known as a PDA, or a computer pen input device.
In an interactive information device having opposing conductive surfaces on a flexible top sheet and a rigid bottom sheet, xe2x80x9cspacer dotsxe2x80x9d, or the like, are non-conductive insulating islands or spacer elements that separate the transparent conductively coated rigid substrate from the flexible transparent conductively coated top sheet in a touch input device when in its normal, untouched condition. When a user presses on the top sheet, such as with a finger or stylus, the flexible transparent conductive substrate is forced to make contact with the transparent conductively coated rigid substrate creating an electrical circuit for touch detection. When the device is not being touched, it is important that the flexible top sheet and the rigid back substrate do not come into contact so as to avoid creating a false touch. It is also desired that the spacer dots or elements be of minimal visibility for optimal optical performance of the information device.
The present invention includes an improved process and improved materials for producing uniformly dispersed, consistent, durable, essentially non-visible, fixed substrate-interpane-spacer elements (for example xe2x80x9cspacer dotsxe2x80x9d) for spacing the opposing conductive surfaces of the flexible top sheet and rigid bottom sheet of an interactive information device.
The invention is most effectively accomplished by the application of the non-conducting spacer dots or elements on the rigid substrate of the interactive information device using appropriately tall dots or elements separating the sheets well apart for optimum electrical performance (non falsexe2x80x94touch) while minimizing visibility for optimum optical performance (such as by rendering the dots invisible such as by index matching the dot material to the surrounding interpane medium and/or by having a small dot diameter and/or by having few, well spaced dots). It is preferred that the performance be further improved by the use of spacer dot materials that are optically matched to the transparent conductors, typically indium tin oxide. It is preferred that the registration and/or orientation of the dots on the glass be matched to the particular touch screen design. It is preferred that the placement of the dots on the glass allow for manufacturability of more than one touch device per coated stock sheet, known as xe2x80x9cstock sheetxe2x80x9d or xe2x80x9cstock litexe2x80x9d form substrates. It is also preferred that the spacer dots be durable to withstand post-processing requirements such as washing, cutting, baking, and the like, for the manufacturing of the touch devices.